/*
 * Copyright (C) 2007 ETH Zurich
 *
 * This file is part of Fosstrak (www.fosstrak.org).
 *
 * Fosstrak is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License version 2.1, as published by the Free Software Foundation.
 *
 * Fosstrak is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with Fosstrak; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA  02110-1301  USA
 */

package org.fosstrak.hal.impl.impinj.comm;

/**
 * CRC8 calculates the CRC8 checksum with polynom x^8 + x^5 + x^4 + x^0 and
 * preset 0x00.
 *
 * @author Jonas Haller
 */

public class CRC8 {
	//	-------- Constants ---------------------------------------------------------
	/** lookup table for CRC */
	static final int CRCtbl[] = {
		0x00, 0x31, 0x62, 0x53, 0xC4, 0xF5, 0xA6, 0x97,
		0xB9, 0x88, 0xDB, 0xEA, 0x7D, 0x4C, 0x1F, 0x2E,
		0x43, 0x72, 0x21, 0x10, 0x87, 0xB6, 0xE5, 0xD4,
		0xFA, 0xCB, 0x98, 0xA9, 0x3E, 0x0F, 0x5C, 0x6D,
		0x86, 0xB7, 0xE4, 0xD5, 0x42, 0x73, 0x20, 0x11,
		0x3F, 0x0E, 0x5D, 0x6C, 0xFB, 0xCA, 0x99, 0xA8,
		0xC5, 0xF4, 0xA7, 0x96, 0x01, 0x30, 0x63, 0x52,
		0x7C, 0x4D, 0x1E, 0x2F, 0xB8, 0x89, 0xDA, 0xEB,
		0x3D, 0x0C, 0x5F, 0x6E, 0xF9, 0xC8, 0x9B, 0xAA,
		0x84, 0xB5, 0xE6, 0xD7, 0x40, 0x71, 0x22, 0x13,
		0x7E, 0x4F, 0x1C, 0x2D, 0xBA, 0x8B, 0xD8, 0xE9,
		0xC7, 0xF6, 0xA5, 0x94, 0x03, 0x32, 0x61, 0x50,
		0xBB, 0x8A, 0xD9, 0xE8, 0x7F, 0x4E, 0x1D, 0x2C,
		0x02, 0x33, 0x60, 0x51, 0xC6, 0xF7, 0xA4, 0x95,
		0xF8, 0xC9, 0x9A, 0xAB, 0x3C, 0x0D, 0x5E, 0x6F,
		0x41, 0x70, 0x23, 0x12, 0x85, 0xB4, 0xE7, 0xD6,
		0x7A, 0x4B, 0x18, 0x29, 0xBE, 0x8F, 0xDC, 0xED,
		0xC3, 0xF2, 0xA1, 0x90, 0x07, 0x36, 0x65, 0x54,
		0x39, 0x08, 0x5B, 0x6A, 0xFD, 0xCC, 0x9F, 0xAE,
		0x80, 0xB1, 0xE2, 0xD3, 0x44, 0x75, 0x26, 0x17,
		0xFC, 0xCD, 0x9E, 0xAF, 0x38, 0x09, 0x5A, 0x6B,
		0x45, 0x74, 0x27, 0x16, 0x81, 0xB0, 0xE3, 0xD2,
		0xBF, 0x8E, 0xDD, 0xEC, 0x7B, 0x4A, 0x19, 0x28,
		0x06, 0x37, 0x64, 0x55, 0xC2, 0xF3, 0xA0, 0x91,
		0x47, 0x76, 0x25, 0x14, 0x83, 0xB2, 0xE1, 0xD0,
		0xFE, 0xCF, 0x9C, 0xAD, 0x3A, 0x0B, 0x58, 0x69,
		0x04, 0x35, 0x66, 0x57, 0xC0, 0xF1, 0xA2, 0x93,
		0xBD, 0x8C, 0xDF, 0xEE, 0x79, 0x48, 0x1B, 0x2A,
		0xC1, 0xF0, 0xA3, 0x92, 0x05, 0x34, 0x67, 0x56,
		0x78, 0x49, 0x1A, 0x2B, 0xBC, 0x8D, 0xDE, 0xEF,
		0x82, 0xB3, 0xE0, 0xD1, 0x46, 0x77, 0x24, 0x15,
		0x3B, 0x0A, 0x59, 0x68, 0xFF, 0xCE, 0x9D, 0xAC
	};

	//	-------- Methods -----------------------------------------------------------
	/**
	 * calculates the checksum.
    *
	 * @param data
    *          the byte-array for which the checksum is to be calculated
	 * @return
    *          a byte containing the checksum
	 */
    public static byte crc8(final byte[] data)
    {
        // CRC preset
        int crc = 0x00;
        for (int i = 0; i < data.length; i++)
        {
            crc = CRCtbl[(crc ^ data[i]) & 0xFF];
        }
        return (byte) (crc & 0xFF);
    }

}
